DTinker is correct. simply switching to red will give you a nasty purplish color because it is not the bulbs that give it the green color, the actual overlay has green integrated into the piece. Apparently to change the color, you need to remove the entire cluster, take it apart, remove the overlay, and very gently sand off the green coloring, then replace the bulbs.

There is a thread that details the entire process if you search for it. Should take a good tech a few hours...